Electric motor housing

ABSTRACT

A housing for an electric motor for driving a fan for a vacuum cleaner, comprising respective parts fitting together so that at least part of the housing comprises spaced inner and outer walls between which exhaust flow of air from the fan takes place, wherein there is provided at least one formation extending into the space between the inner and outer walls to cause the air to flow in an elongated flow path therebetween.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom application number0606838.1 filed on Apr. 5, 2006, the entirety of which is fullyincorporated by reference herein.

BACKGROUND

This invention relates to a housing for an electric motor, intended foruse for driving a fan in a vacuum cleaner, although it may haveapplications in other appliances or devices.

In order to create the volume of air flow necessary for effectivecleaning, vacuum cleaners use fans or impellers driven by relativelypowerful electric motors. Typically, vacuum cleaners for domestic usemay include motors whose power is in the range 1 kw to 2 kw. Forreliable operation of such a motor, which usually will be accommodatedin a relatively small space in a cleaner's body, effective cooling isnecessary for and this is generally achieved, at least in vacuumcleaners for “dry” use, by providing for the flow of air to pass atleast around, and in most cases through the interior of, the motor. Thusin typical vacuum cleaners the flow of cleaning air, having entered thevacuum cleaner directly from a cleaning head (in the case of an“upright” type of cleaner) or by way of a suction hose (in the case of a“cylinder” type of cleaner or an upright cleaner having a hose) passesfirstly to a dust separating/collecting device of the cleaner, which byuse of one or more cyclonic separating devices and/or filters separatesentrained dust and dirt from the air flow and retains it for laterdisposal. From the separating device, the air is drawn to the fan(usually through a pre-motor filter, which ensures that air passingthrough the motor is as clean as possible), and thence through the motorand is expelled to the external atmosphere from the cleaner. There maybe a final, post-motor, filter to ensure that little or no dust, forexample dust from the motor or dust which somehow has escaped theseparating device and pre-motor filter, is released to the externalatmosphere.

There are also electric motors of the so-called “by-pass” type,typically used in “wet” vacuum cleaners which are able to draw upliquids, and in appliances such as extractor carpet cleaners which applycleaning liquid and then extract it by suction from the cleaned carpet,in which the suction air flow created by the motor does not pass throughthe motor for cooling purposes but instead the motor is cooled by aseparately-induced flow or air drawn from a position where liquid cannotbe expected to be encountered. The present invention has been devised inrelation to installations of electric motors of the first-mentionedkind, i.e. in which the flow of air caused by the suction-producing fanpasses through the motor.

The use of powerful motors and fans, causing high air flow speeds,inevitably generates substantial noise. One important aspect of vacuumcleaner design is minimising the level of noise created in the vicinityof a cleaner while it is in operation. Since in the path of flow of airin a vacuum cleaner the motor is usually immediately before the air isexhausted from a cleaner (albeit possibly with a final exhaust filter toensure as few particles as possible are entrained in the exhaust airflow), flow of air through and around the motor is very significant interms of the overall noise level. Therefore attention has been directedto minimising the generation of noise in this area; one solution whichhas been adopted is for the motor to be disposed in a housing of whichat least part has a double-wall construction with a space between innerand outer walls, through which exhaust air flows from the motor,containing a wadding material. This substantially reduces noiseemission. However, such a construction is expensive, and presents someunwanted resistance to flow of air.

SUMMARY

It is broadly the object of the present invention to address theabove-described problem of noise emission, in an improved manner.

According to one aspect of the invention, we provide a housing for anelectric motor for driving a fan for a vacuum cleaner, the housingcomprising respective parts fitting together so that at least part ofthe housing comprises spaced inner and outer walls between which exhaustflow of air from the fan takes place, wherein there is provided at leastone formation extending into the space between the inner and outer wallsto cause the air to flow in an elongated flow path therebetween.

The spaced inner and outer walls may each be generally cylindrical sothat an annular space is defined therebetween for flow of air. The“straight-line” flow of air therebetween would be in the axial directionthrough the annular space, and in accordance with the invention someflow of air may be caused in the direction circumferentially of such anannular space.

The causing of air to flow in an elongated flow path in the spacebetween the inner and outer walls of the housing causes a significantreduction in the sound level created by such flow. At the same time, anunacceptable resistance to the flow of air need not be created, as longas a highly-labyrinthine flow path is not established.

The formation or formations which cause the air to flow in the elongatedflow path may comprise at least one rib or vane extending from one ormore of the housing parts into the space between the inner and outerwalls thereof.

The at least one rib or vane may be part-helical in configuration, sothat the flow path for air is at least partially helical, through theannular space.

Four of the rib or vane formations may be provided, each having acircumferential extent of approximately a quarter of the annular spacebetween the inner and outer walls.

DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference tothe accompanying drawings, of which:

FIG. 1 is a side view of a vacuum cleaner.

FIG. 2 is a plan view of the vacuum cleaner of FIG. 1.

FIG. 3 is a partial exploded view of an electric motor housing for usewith the vacuum cleaner of FIG. 1.

FIG. 4 is a perspective of the motor housing of FIG. 3.

FIG. 5 is a partial section view of the motor housing of FIG. 3.

FIG. 6 is another partial section view of the motor housing of FIG. 3

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring firstly to FIGS. 1 and 2 of the drawings, these depict avacuum cleaner of the “cylinder” type, wherein the invention can beutilised. It comprises a body 10 having a pair of wheels 11, 12 onopposite sides of the body at a rear portion thereof, to enable the bodyto be moved over a floor surface as required. Although not shown in thedrawings, there would also be provided a front wheel or wheels beneaththe body towards the opposite, front end thereof. Also towards the frontend thereof, the body accommodates a removable separator/collectorassembly indicated generally at 14, for separating entrained dust anddirt from the suction air flow being drawn from whatever is beingcleaned, and retaining such dust and dirt for later disposal. One ormore cyclonic separator devices and/or filters may be utilised in theseparator/collector. Shown in FIG. 2 is an inlet aperture 16 in theseparator/collector assembly 14 for connection of a flexible suctionhose whose other end has an inlet fitting for direct use as a suctionnozzle, or connection to a wand or cleaning head, in known manner.

The suction air flow for cleaning as aforesaid is created by an electricmotor and fan assembly which may be disposed where indicated at 18,generally in the rear part of the body 10 of the cleaner, between thewheels 11, 12 thereof. A passage extends from the fan in the assembly 18to a port which communicates with an outlet port of theseparator/collector assembly 14, for outflow of the suction airflowafter the separation of entrained dust and dirt therefrom in theassembly 14.

A pre-motor filter would be provided either in the body 10 of thecleaner or in the separator/collector assembly 14 for cleaning of thesuction air flow before it passes to the motor and fan assembly 18. Fromthe assembly 18, air is expelled to the external atmosphere, possibly byway of an exit filter so that little or no remaining dust is expelled tothe external atmosphere.

Referring now to FIGS. 3, 4, 5 and 6 of the drawings, these illustratein exploded, cut away, and sectional views the arrangement of theelectric motor and fan of the vacuum cleaner in relation to a housingtherefor.

FIG. 3 shows the housing for the motor comprising first and secondhousing parts 20, 22 and a cover ring 24. The first housing part 20 isgenerally cup-shaped in configuration, with a generally cylindricalperipheral wall 26 stepped down in diameter as shown at 28, 30 leadingto an annular end wall 32 which, as seen in FIG. 5, has an opening 34therein. At the opposite end of the peripheral wall 26 there is a flangeformation 36. The opening 34 provides for inflow of suction air to anassembly of an electric motor and fan, the casing of whose fan isindicated at 37 in FIGS. 4 and 5 and the casing of whose motor isindicated at 38. The fan casing 37 has an opening 40 for inflow of airto the fan within the casing, such opening 40 facing the opening 34 inthe wall 32.

Also visible in FIG. 3 of the drawings is an opening 42 in a portion 44extending from the wall 28, for receiving a relief valve to admit airfrom the external atmosphere to the fan inlet opening 40 in case thenormal path for suction air flow becomes blocked, e.g. by the ingestionof a blocking object into the cleaning head, suction hose, orseparator/collector, so that under such circumstances the motor is notdeprived of cooling air flow.

The second housing part 22 is a generally cup-shaped component but ofsmaller axial extent than the housing part 20. The part 22 comprises aperipheral wall 46 of generally cylindrical configuration, and an endwall 48 closing the housing part 22 at its end remote from the end wall32 of the housing part 20. The motor and fan assembly 37, 38 is heldbetween the housing parts 20, 22, the fan casing 37 being rubber-mountedwithin the wall portion 28 of the housing part 20 and the opposite endof the casing 38 of the motor being rubber mounted within a boss 50 onthe wall 48 of the housing part 22. The housing part 22 is secured tothe housing part 20 by four circumferentially spaced outwardly extendinglugs as indicated at 52, 53, 54, 55 provided on the housing part 22where the peripheral wall 46 joins the end wall 48 thereof. The lugs 52to 55 are received in recesses in the flange 36 of the housing part 20,such recesses being indicated at 56 to 59, and support the two housingparts relative to one another so that the peripheral wall 46 is spacedinwardly of the peripheral wall part 26, with an annular space definedtherebetween.

With the housing parts 20, 22 fitted together as aforesaid, the coverring 24 is fitted as shown in FIGS. 4 and 5, engaging the flange part 36of the housing part 20 and holding the lugs 52 to 55 in the recesses 56to 59. The cover ring 24 is secured by circumferentially spaced axiallyextending screws, each passing through a hole in the ring 24, an alignedhole in the respective lug e.g. as indicated at 62 in relation to thelug 52, and having engagement with a bore at the base of the recess inthe housing part 20 as indicated at 64 in relation to the recess 56. Thecover ring has a cylindrical wall portion 25 which may accommodate orco-operate with a post-motor filter.

The peripheral wall 46 of the housing part 22 is provided with fourcircumferentially spaced ribs or vanes which extend radially outwardlyfrom the wall 46 to touch or very nearly touch the internal surface ofthe peripheral wall part 26 of the housing part 20. Three of such ribsare visible at 66, 68, 70 with the shape of the rib 68 beingparticularly clearly visible in FIG. 5. It will be noted that it extendsgenerally helically but of variable curvature, from the free end of theperipheral wall 46 of the housing part 22, to a base part of the lug 54approximately two thirds of the distance to the end wall 48 of thehousing part 22. The arrangement of the ribs and lugs is such that aircannot flow axially in a straight line from one end to the other of theannular space defined between the peripheral walls 26, 46 of the twohousing parts 22 but instead is forced to extend its flow path in agenerally helical configuration.

Thus, the flow of air through the motor and fan assembly is as shown bythe heavy arrows on FIGS. 5 and 6. After entering the fan casing atopening 40, the air flows through the fan and the motor to leave themotor at the end thereof remote from the fan, and then flows in theopposite direction, towards the fan casing, in an annular space definedbetween the motor casing 38 and the wall 46 of the housing part 22.Having flowed past the motor casing, it flows in a generally helicalpath through the annular space between the walls 26, 46 guided by theribs in such space. It then exits the motor housing assembly through thecentre of the ring 24.

The above described path of air flow subsequent to having passed throughthe fan has a silencing effect, without providing an undue restrictionto such flow of air. The construction of the housing is straightforward, and the provision of wadding material or the like forquietening purposes is unnecessary.

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

1-11. (canceled)
 12. A housing for an electric motor driving a vacuumcleaner fan, comprising spaced inner and outer walls receiving exhaustair flow from a fan, and at least one formation extending into a spacebetween the inner and outer walls to define an elongated flow paththerebetween.
 13. A housing of claim 12, wherein the spaced inner andouter walls are generally cylindrical defining an annular spacetherebetween.
 14. The housing of claim 13, wherein at least a portion ofthe air flow is in a circumferential direction within the annular space.15. The housing of claim 14, wherein at least a portion of the air flowis in a helical direction within the annular space.
 16. The housing ofclaim 12, wherein the at least one formation comprises at least one ribor vane extending from one of the inner and outer walls into the spacebetween the inner and outer walls thereof.
 17. The housing of claim 16,wherein the at least one rib or vane is at least partially helical. 18.The housing according to claim 16, wherein the at least one rib or vanecomprises four ribs or vanes that are substantially evenly spaced apartalong the circumference of the inner wall.
 19. The housing of claim 12,further comprising an electric motor provided within the housing forrotating the fan.
 20. The housing of claim 12, wherein the formationextends radially from the inner wall toward the outer wall.
 21. Thehousing of claim 20, wherein the formation contacts or is insubstantially close proximity to the outer wall.
 22. The housing ofclaim 16, wherein the at least one rib or vane extends radially andhelically from the inner wall toward the outer wall.
 23. The housing ofclaim 22, wherein the at least one rib or vane extends at a varyingcurvature along the length inner wall.
 24. The housing of claim 12,wherein the formation extends along approximately two thirds of a lengthof the inner wall.
 25. The housing of claim 12, wherein the formationengages a lug that extends radially outward from the inner wall, the lugconnecting the inner wall to the outer wall.